March 17, 2009

The self-healing coating uses chitosan, a substance found in the shells of crabs and shrimp. This is incorporated into traditional polymer materials, such as those used in coatings on cars to protect paint.

When a scratch damages the chemical structure, the chitosan responds to ultraviolet light by forming chemical chains that begin bonding with other materials in the substance, eventually smoothing the scratch. The process can take less than an hour.

But:

The team tested the compound’s properties using a razor-blade-thin scratch. “We haven’t done any of the tests to show how wide it can be,” Urban said in a telephone interview.

He said the polymer can only repair itself in the same spot once, and would not work after repeated scratches.

“Obviously, this is one of the drawbacks,” he said, adding that the chances are low of having two scratches in exactly the same spot.